A novel form of tumor antigen, termed Large Multivalent Immunogen (LMI), has been found to enhance in vivo tumor-specific cytolytic responses, and to significantly reduce tumor growth and extend survival of tumor-bearing animals. LMI are prepared by isolating tumor cell surface membranes and immobilizing these on cell-size microspheres. Work done under Phase I of this project has established the novel ability of LMI to mediate tumor reduction, in comparison to other forms of antigen, and demonstrated that treatment of mice bearing established, progressing P815 (mastocytoma) solid tumor with a combination of cyclophosphamide and LMI results in long term survival of the majority of the mice. Phase II of this project has two major goals; to study the mechanism(s) by which LMI treatment reduces tumor growth, and to develop LMI technology for use in humans and obtain data needed to initiate clinical trials. This will include development of a non-toxic, biodegradable support material for preparation of LMI, and in vitro studies of LMI-mediated activation of cloned human cytolytic T lymphocytes (CTL) specific for melanoma antigens. We anticipate being able to initiate a clinical trial with melanoma patients by the end of this Phase II project, and possibly sooner.